Cannot put complex signal on expandable (bus) connector

[Christian Kral <dr.christian.kral@…>]

Consider the following example

package ComplexBus
  extends Modelica.Icons.Package;
  model Example
    extends Modelica.Icons.Example;
    Bus bus annotation (Placement(transformation(extent={{-10,-10},{10,10}}), iconTransformation(extent={{-10,-10},{10,10}})));
    Modelica.ComplexBlocks.Sources.ComplexConstant const(k(re=1, im=2))
                                                         annotation (Placement(transformation(extent={{-60,-10},{-40,10}})));
  equation 
    connect(const.y, bus.compl) annotation (Line(points={{-39,0},{-19.5,0},{0,0}}, color={85,170,255}), Text(
        string="%second",
        index=1,
        extent={{6,3},{6,3}}));
    annotation (Icon(coordinateSystem(preserveAspectRatio=false)), Diagram(coordinateSystem(preserveAspectRatio=false)));
  end Example;

  expandable connector Bus
    extends Modelica.Icons.SignalBus;
    annotation (Icon(coordinateSystem(preserveAspectRatio=false)), Diagram(coordinateSystem(preserveAspectRatio=false)));
  end Bus;
  annotation (uses(Modelica(version="3.2.2")));
end ComplexBus;

When checking ComplexBus.Example the following error message is triggered:

[1] 22:18:33 Translation Error
[ComplexBus: 10:5-13:31]: Failed to instantiate equation 
connect(const.y, bus.compl) annotation(Text(string = "%second", index = 1, extent = {{6, 3}, {6, 3}}));.

[2] 22:18:33 Translation Error
Error occurred while flattening model ComplexBus.Example

Consequently, the example model cannot be simulated.

The error occurs using:

OMEdit 1.12.0~dev-154-g354a8d1
Connected to OpenModelica 1.12.0~dev-321-g9addb54
Linux Mint 18.1 64bit

[Christian Kral <dr.christian.kral@…>]

Even after removing the text from the annotation the error remains:

package ComplexBus
  extends Modelica.Icons.Package;
  model Example
    extends Modelica.Icons.Example;
    Bus bus annotation (Placement(transformation(extent={{-10,-10},{10,10}}), iconTransformation(extent={{-10,-10},{10,10}})));
    Modelica.ComplexBlocks.Sources.ComplexConstant const(k(re=1, im=2))
      annotation (Placement(transformation(extent={{-60,-10},{-40,10}})));
  equation 
    connect(const.y, bus.compl) annotation (Line(points={{-39,0},{-19.5,0},{0,0}}, color={85,170,255}));
    annotation (Icon(coordinateSystem(preserveAspectRatio=false)), Diagram(coordinateSystem(preserveAspectRatio=false)));
  end Example;

  expandable connector Bus
    extends Modelica.Icons.SignalBus;
    annotation (Icon(coordinateSystem(preserveAspectRatio=false)), Diagram(coordinateSystem(preserveAspectRatio=false)));
  end Bus;
  annotation (uses(Modelica(version="3.2.2")));
end ComplexBus;

Check of ComplexBus.Example leads to

[1] 22:25:21 Translation Error
[ComplexBus: 10:5-10:104]: Failed to instantiate equation 
connect(const.y, bus.compl);.

[2] 22:25:21 Translation Error
Error occurred while flattening model ComplexBus.Example

[Adrian Pop]

The specification says that the expandable connectors can contain only scalar variables and other connectors.
Is unclear if you can connect a record or a complex type to the expandable connectors.
However, we should consider this anyway. What happens if you connect the "im" and "re" to the bus?

[Christian Kral <dr.christian.kral@…>]

Thanks for the hint. In the MSL specification 3.3 revision 1 it reads on page 101:

Before generating connection equations non-parameter scalar variables and non-parameter array elements declared in expandable connectors are marked as only being potentially present. A non-parameter array element may be declared with array dimensions “:” indicating that the size is unknown. This applies to both variables of simple types, and variables of structured types.

Is this the paragraph you refer to?

One alternative implementation were to specify the complex quantity on the bus class definition

  expandable connector Bus
    extends Modelica.Icons.SignalBus;
    Complex compl;
  end Bus;

This should then be in line with the Modelica specification and OpenModelica simulates the example then with no complaints.

Unfortunately we cannot simply change the structure from one complex variable to two real variables due to backwards compatibility reasons.

[Christian Kral <dr.christian.kral@…>]

For now I am happy with the current status as there exists a workaround.

[Adrian Pop]

Please leave it open so we don't forget about it. I'll change the priority to low.

[Adeel Asghar]

Maybe we should also move it to a proper component.

[Per Östlund]

Fixed, see ​https://github.com/OpenModelica/OpenModelica/pull/10540